Helical antenna with transversely extending, top-loading straight antenna in series therewith



1966 v c. SMITH, JR, ETAL 3,

HELIGAL ANTENNA WI TH TRANSVERSELY EXTENDING, TOP-LOADING STRAIGHT ANTENNA IN SERIES THEREWITH Filed June 11, 1962 5 Sheets-Sheet 1 TRANSMITTER RECEIVER VALOR C. SMITH JR., LAN JEN CHU INVENTORS BY mwm ATTORNEYS V. C. SMITH, JR.. ETAL HELICAL ANTENNA WITH TRANSVERSELY EXTENDING,

Filed June 11, 1962 Feb. 15, 1966 3,235,871 TUB-LOADING STRAIGHT ANTENNA IN SERIES THEREWITH 5 Sheets-Sheet 2 FIG. IB

FIG.

vALoR c. SMITH JR.,

LAN JEN CHU INVENTORS ATTORNEYS Feb. 15, 1966 V. C. SMITH, JR., ETAL HELICAL ANTENNA WITH TRANSVERSELY EXTENDING, TOP-LOADING STRAIGHT ANTENNA IN SERIES THEREWITH Filed June 11, 1962 IIIIII lllllllflllllllll FIG.

5 Sheets-Sheet 4 VALOR 0. SMITH JR., 3 LAN JEN CHU INVENTORS 10' ATTORNEYS 1966 v. c. SMITH, JR.. ETAL 3,235,871 HELICAL ANTENNA WITH TRANS SELY EXTENDING, TOP-LOADING STRAIGHT ANTENNA SERIES THEREWITH Filed June 11, 1962 5 Sheets-Sheet 5 X g X VALOR 0. SMITH JR., 3 25 24 LAN JEN CHU INVENTORS BY i 5 ATTORNEYS FIG. 4

United States Patent 3,235,871 HELICAL ANTENNA WITH TRANSVERSELY EX- TENDIN G, TOP-LOADIN G STRAIGHT ANTENNA IN SERIES THEREWITH Valor C. Smith, Jr., El Cajon, Calif., and Lan Jen Chu, 18 Oakmont Circle, Lexington, Mass.; said Smith assignor to said Chu Filed June 11, 1962, Ser. No. 201,370 2 Claims. (Cl. 343895) The present invention relates to transmitting and receiving antennas and, more specifically, to antennas of the helical type.

Numerous varieties of helically wound antennas have been proposed and utilized for different radiating and receiving functions in the communication art. Such antennas, however, are inherently difiicult to tune over wide frequency bands and, Where tunable, require complicated separate tuning structures, usually in the form of direct sliding contacts. Problems, including impedance matching, in connection with the types of feed lines customarily used to connect with helical antennas (the term feed being herein used in its generic sense to embrace both transmission and reception), have also plagued the art, particularly where frequency variation has been required.

An object of the present invention, accordingly, is to provide a new and improved helical antenna construction that admirably solves the wide-band tuning, feeding, and impedance-matching problems above-discussed.

Still another object is to provide an antenna of the character described that is also particularly suited to such purposes as submarine communication; in which application, the advantages of a free-flooding design void of requirements for moving pressure seals and a separate tuner are attained.

A further object is to provide a novel antenna of more general character, as well, providing less size than conventional equivalent whip antennas, greater power handling capability due to a low-impedance input and a grounded antenna base, and a balanced input antenna feed.

Other and further objects will be explained hereinafter and will be more particularly pointed out in connection with the appended claims. In summary, however, from one of its broad aspects, the invention contemplates a helically wound antenna provided, preferably, with a substantially coaxially disposed feed loop, the plane of which loop may be variably oriented, and means for effectively shorting predetermined turns of the antenna.

The invention will now be described in connection with the accompanying drawings, FIG. 1 of which is a schematic diagram of a helical antenna constructed in accordance with a preferred embodiment of the invention;

FIGS. 1A and 1C are respectively longitudinal-sectional and front elevational views of modifications;

FIG. 1B is a diagram similar to FIG. 1, but upon a reduced scale, of a further modification;

FIG. 2 is a longitudinal section of a practical embodiment of the form of the invention shown in FIG. 1, illustrating the antenna in an extended position;

FIG. 3 is a view similar to FIG. 2 of the antenna in a retracted position; and

FIG. 4 is a similar view, upon an enlarged scale, of the feed-loop rotating mechanism of the antenna of FIGS. 2 and 3.

Referring to FIG. 1, the antenna is shown in the form of the helical winding 1, having a substantially coaxially disposed feed loop 2 disposed therewithin; the feed loop 2 being a split loop fed from a transmitter and/or receiver 4 by a coaxial line 3-3. The inner coaxial line conductor 3' passes within the right-hand hollow part of Patented Feb. 15, 1966 ice the loop 2 and connects at 2' with the left-hand portion of the split loop, with the outer conductor 3 grounded at G. While the feed loop 2 is illustrated as a single turn, it may comprise any number ofturns, one above the other, depending on the impedance desired, as more particularly shown in FIGS. 1A and 1C. Preferably, though not essentially in all cases, the plane of the feed loop 2 is rotatable or pivotable, as later discussed, from a substantially horizontal plane, for a maximum magnetic coupling, to a substantially vertical plane for substantially negligible magnetic coupling, being shown in FIG. 1 oriented at an angle 0:.

Since the impedance of the antenna is determined, in a principal manner, by the mutual coupling between the feed loop 2 and the helical winding 1, adjustment of the same, as for different frequencies, may be readily effected by rotating or tilting the feed loop 2 through the required angle a.

Tuning of the antenna to any particular frequency is accomplished by adjusting the inductance of the helical winding 1 and its capacitance to ground G, Where the term ground may apply not only to actual earthing, but to, for example, the hull of a submarine or the like. This may be effected by upward movement of a conductive grounded sleeve 5, which may be disposed outside, but is prefer-ably within, the winding 1, and either contacts the same or is closely coupled to the winding to effect short-circuiting of a predetermined number of turns, depending upon the degree of upward insertion or movement of the sleeve 5, thus varying the inductance of the helical winding 1 and its capacitance to ground.

A practical helical antenna 0 fthe type shown schematically in FIG. 1 is illustrated in FIGS. 2 through 4, the particular embodiment being adapted especially for submarine and related installations, but not being restricted to such applications.

The hull of a submarine is shown represented by a line marked 6 in FIG. 3, and the top of the fairwater thereof by a line marked 7 also in FIG. 3.

The helical winding 1 is embedded in a column of binding material 1 such as a tubular Fiberglas laminate. When not in use, the antenna is stored within a mast 10 contained inside the fairwater 7, as shown in FIG. 3. The helical Winding 1 and the mast 10 may be raised from the retracted position of FIG. 3 to a fully extended operating position, as shown particularly in FIG. 2, by any conventional mechanism, such as that used for periscope retraction and extension, not shown in the drawing since such mechanism constitutes no part of the present invention and it is not desired unduly to complicate the drawing. The helical winding 1, however, will be guided in its axial retracting or extending movement by a pair of sleeves 27 and 28.

Tuning of the thus-extended antenna is effected by raising or lowering the internal coaxially disposed shorting sleeve 5. An enclosure 12 that contains the feed loop 2 at its upper end is shown connected in fixed relationship with the shorting sleeve 5, to move as a unit therewith, if desired.

The feed loop 2, as more particularly shown in FIG. 4, may be rotated or oriented for impedance matching and the like, as before mentioned, by a shaft 13, to which the feed loop 2 is secured. The shaft 13 is driven through a pair of bevel gears 14 and 15 by a further shaft 16 that is coupled at 17 to still a further shaft 18. The shaft 18 is, in turn, driven through a gear 19 by a drive motor 20. Electric power for the drive motor 20 is carried through a power cable 11, FIGS. 2 and 3, through a pressure-tight connector 24, FIGS. 2, 3 and 4, and thence by way of conductors 22, FIG. 4, to the drive motor 20. Another conductor 23, FIG. 4, extending from the connector 24,

carries power to a synchro-pick-up 21 which registers the different angular positions cc of the plane of the feed loop 2. The radio-frequency feed line 3, 3 to the feed loop 2 passes through a further pressure-tight connector 25 and thence to the feed loop 2 in the manner illustrated in FIG. 1. The enclosure 12 containing the feed loop 2 at its upper end is a water-proof capsule which protects the enclosure when the entire unit is flooded during some types of operation of the submarine. Water drains 31, FIG. 2, enable the escape of water during or after such flooding, and the unit is capped at 30 and sealed, when retracted, at 32 to a cover 29.

Reference has been made previously to the shorting sleeve 5, and it is now in order to describe a mechanism by which axial movement thereof is effected for tuning. A traveling nut 9, FIGS. 2 and 3, is secured to the shorting sleeve 5 and engages a threaded shaft 8. When the threaded shaft 8 is rotated in a manner to be hereinafter described, the traveling nut 9 threads axially up or down the threaded shaft 8, as the case may be, carrying with it the shorting sleeve 5. A hearing 26 acts radially to position the threaded shaft 8, and downward thrust upon the threaded shaft 8, and due to the weight of the shorting sleeve 5 and the threaded shaft itself, is accommodated by a thrust bearing 14', FIG. 3. Rotation of the threaded shaft 8 may be effected by an electric or hydraulic motor, not shown, through a shaft 10, FIG. 3, bevel gears 11 and 12', and a further shaft 13, which is secured to the threaded shaft 8, as by keying.

In the modification of FIG. 1A, multiple-turn feed loop 2 is disposed near the bottom of the helical winding 1 and a crank 8' permits movement of the shaft 8 to move the shorting tuning sleeve 5 up and down near the upper end of the antenna 1. A supplemental whip antenna 1" is shown pivotally or swively connected at 50 to the upper portion of the sleeve 5 to constitute a supplemental straight radiating top-loaded antenna element in series with the helical antenna 1, as for emergency use.

The supplemental antenna 1 is also shown in FIG. 1B, in the form of a horizontal extension that is grounded at its free end G.

In the system of FIG. 1C, on the other band, the feed loop 2 is substantially coaxially coupled to the winding 1 at an external position rather than within the helical winding.

Further modifications will also occur to those skilled in the art and all such are considered to fall within the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A helically wound antenna having means extending from near its lower end for feeding the antenna, a shorting mechanism adjustable to short-circuit successive windings of the antenna from the top end downwards, and a top-loading substantially straight antenna series connected to the said top end of the helical antenna and extending therefrom transversely of the longitudinal axis of the helical antenna, said straight antenna being grounded at its end remote from the said top end of the helical antenna.

2. An antenna as claimed in claim 1 and in which the feeding means is constituted solely by magnetically coupled loop means.

References Cited by the Examiner UNITED STATES PATENTS 2,781,514 2/1957 Sichak et al 343-895 2,866,197 12/1958 Kandoian 343895 2,875,443 2/1959 Kandoian 343-895 3,098,230 7/1963 Nickerson et al. 343850 FOREIGN PATENTS 411,888 7/1945 Italy.

HERMAN KARL SAALBACH, Primary Examiner. 

1. A HELICALLY WOUND ANTENNA HAVING MEANS EXTENDING FROM NEAR ITS LOWER END FOR FEEDING THE ANTENNA, A SHORTING MECHANISM ADJUSTABLE TO SHORT-CIRCUIT SUCCESSIVE WINDINGS OF THE ANTENNA FROM THE TOP END DOWNWARDS, AND A TOP-LOADING SUBSTANTIALLY STRAIGHT ANTENNA SERIES CONNECTED TO THE SAID TOP END OF THE HELICAL ANTENNA AND EXTENDING THEREFROM TRANSVERSELY OF THE LONGITUDINAL AXIS OF THE HELICAL ANTENNA, SAID STRAIGHT ANTENNA BEING GROUNDED AT ITS END REMOTE FROM THE SAID TOP END OF THE HELICAL ANTENNA. 